1. Field of the Invention
The present invention relates to a method for the preparation of 1-terpinen-4-ol, 1(7)-terpinen-4-ol, and intermediates thereof.
2. Brief Description of the Prior Art
1-Terpinen-4-ol is a fragrance chemical possessing a pleasing earthy-green note with a slightly peppery-woody undernote. It is an important constituent of synthetic essential oils, especially geranium, lavender, and rose oils and has the desirable effect in all fragrance compositions of enhancing naturalness and diffusiveness. Because of the high cost and uncertainty of supply of the natural product, which is isolated from tea tree oil, synthetic routes to 1-terpinen-4-ol have been developed, notably via photo-oxidation or epoxidation of terpinolene. Both of these processes suffer from only modest overall yields and multiple chemical steps. The photochemical route requires expensive specialized equipment.
1(7)-terpinen-4-ol is a minor constituent of rosemary oil and occurs in trace quantity in commercial pine oil, which consists of mainly alpha-, beta-, and gamma-terpineols; see J. Org. Chem., 31, 2419 (1966). It is not available in good purity from either natural or synthetic sources. It is rarely mentioned in the chemical literature, and its unambiguous synthesis has been described only once [Indian J. Chem., 9(9), 899,1971]. This laboratory synthesis involved four steps and required expensive mercury- and phosphorous-containing reagents. The overall molar yield was only 22%.
The procedure of the present invention has three major advantages over the prior art preparations. First, it is a single step process. Second, it proceeds in very high selectivity to either or both of the desired 4-ol products, depending on the reaction conditions. Third, it uses as starting material a low-cost by-product, namely, 1,4-cineole, which is generated during the production of pine oil by hydration of the abundant turpentine component, alpha-pinene.